WHen i do
Then i get the list of all processes , Is there any tutorial which explains which process is doing what
ps -A x will list the processes as well as the command line arguments used (which is really useful). netstat -tup will list all tcp and udp connections as well as the process driving those connections. Run as root if some process ids are blanked out. lsof -p pid will list all the open handles currently owned by the process associated with pid. This information usually encapsulates files and sockets, very useful for figuring if a process has got a lock on a file. grep, awk, sort and uniq are great tools for ordering and filtering the data generated by the ps, netstat and lsof commands.
Usually you'll get an idea what each process does in its man page. Just run
Processes shown within square brackets in the output of